Pilot-operated shut-off valve

ABSTRACT

An automatic pilot-operated shut-off valve including, in the pilot valve assembly, a pilot piston which controls the operation of oppositely disposed admission and discharge valves. An additional flow control device, in the form of a spool valve, is disposed in the pilot piston for the purpose of restricting the flow between the ends thereof during the discharge valve opening cycle.

United States Patent 1 Huet Nov. 13, 1973 [54] PILOT-OPERATED SHUT-OFF VALVE 2,649,115 8/1953 Deardorff 137/488 [76] Inventor: Paul Huet, 65 Rue Michel-Ange,

Paris, France Primary Examiner-Henry T. Klinksiek [22] Filed: Oct. 30 1972 Attorney-David S. Fishman et a1.

[21] Appl. No.: 302,197

[57] ABSTRACT 30 F i A ll t P t 1 0 pp ca [on y Data An automatic pilot-operated shut-off valve including,

ct. 71 France 7139153 I in the pilot valve embly, a pilot piston which 6011- trols the operation of oppositely disposed admission (g1. and discharge valves An additional flow control E i 1 vice, in the form of a spool valve, is disposed in the 0 care pilot piston for the purpose of restricting the flow bel References Cited tween the ends thereof during the discharge va ve opening cycle.

5 Claims, 3 Drawing Figures Patented Nov. 13,1973 3,771,5s3

3 Sheets-Shoot 1 Patented Nov. 13, 1973 3 Shoots-Shoot :3

FIG. 3-

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PILOT-OPERATED SHUT-OFF VALVE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the control of the application of a pressurized fluid to a load. More specifically, this invention is directed to automatic pilotoperated shut-off valve devices. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.

2. Description of the Prior Art Automatic pilot-operated shut-off valve devices are known in the art. The prior art devices have included, in a pilot valve circuit, a pair of shut-off valves; these shut-off valves respectively controlling the admission of control fluid to an actuator for the primary flow controller and the discharge or venting of control fiuid from the actuator. Previously available pilot-operated shut-off valves have included means, usually combined with the admission shut-off valve portion of the pilot valve assembly, for throttling flow during the initial opening or unsticking period. Field experience has, however, proven these throttling devices to be lacking in reliability.

To briefly state the desired attributes of an automatic pilot-operated shut-off valve, which attributes have not been completely satisfied by prior art devices, the pilot valve should open instantaneously at the pressure for which the pilot is calibrated. Additionally, the pilot valve assembly. should be characterized by no leakage through either of the two shut-off valves in their closed position. Also, the main shut-off valve should be operated in response to a pressure variation on the order of 2% of the normal supply pressure.

SUMMARY OF THE INVENTION The present invention overcomes the above briefly discussed and other disadvantages of the prior art by providing a novel and improved automatic pilotoperated shut-off valve device possessing the abovestated desirable attributes of such devices. In accordance with the present invention the device which has previously unreliably throttled the axial passage in the pilot piston of prior art devices during the lift period has been replaced by a throttle or restrictor device which is independent of the movements of the pilot piston. The foregoing objective has been achieved by incorporating, inside the pilot piston, a spool valve which restricts the flow between the chambers at the opposite ends of the pilot piston during the lift period. The oppositely disposed ends of the spool member of this pilot piston installed spool valve are respectively subjected to the pressures prevailing in the said two end chambers. Through the use of this spool valve, constant throttling is insured during the lift period and, after this period and as a consequence of the pressure difference between the two chambers, complete opening of the axial passage through the pilot valve piston between the two chambers is achieved.

BRIEF DESCRIPTION OF THE DRAWING:

The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals jet defining member 10.

refer to like elements in the several figures and in which:

FIG. 1 is a side elevation view of a first embodiment of the invention, the main shut-off valve portion of the disclosed embodiment being shown partially in section in FIG. 1;

FIG. 2 is a cross-sectional, side elevation view of the pilot valve of the FIG. 1 embodiment; and

FIG. 3 is an enlarged cross-sectional view of a portion of the pilot valve of FIG. 2.

DESCRIPTION or THE PREFERRED EMBODIMENT:

With reference to FIG. 1, a main shut-off valve is indicated generally at l and shown in cross-section. Main shut-off valve 1 is responsible for securing pressure and flow to a load. The operation of valve 1 is controlled by means of a pilot valve which has been indicated generally at 2.

Considering briefly main shut-off valve 1, this flow controlling device comprises a body 9, a jet or inlet passage defining member 10 and a flange plate 13. Plate 13 is machined to define a bore which receives a conduit or probe 17; fluid for operating the pilot valve being tapped off the main flow path via conduit 17. Shut-off valve 1 further comprises a floating valve member 8 which cooperates with the upper end of jet 10 to perform the valving action; valve member 8 which may have a spherical surface which cooperates with a conical seating surface on jet 10 whereby the valve aligns itself and seats properly on the jet. Valve member 8 is attached to a piston 6 by means of a retaining member 7. Piston 6 travels within a piston guide member 4. Sealing between piston 6 and guide 4 is effected by means of a toroidal seal 5. j

The subassembly comprising the piston guide 4, piston 6 and an end cover 3 defines an upper chamber 47; cover 3 being bolted to body 9 to complete the main shut-off valve assembly. Fluid delivered to upper chamber 47 of valve 1, in the manner to be described below, acts upon piston 6 to close and thereafter hold the main shut-off valve closed by urging valve member 8 against Referring now to FIG. 2, the pilot valve 2 is comprised of three principal subassemblies. The first of these subassemblies is contained within an elongated upper end cover 21. The second subassembly is contained within a central body portion 28 of the pilot valve. The third major subassembly of pilot valve 1 is defined by and contained within a base member 36.

Considering first the upper subassembly of pilot valve 2, the upper end cover 21 is threadably engaged with the main body portion 28 and, through the use of cooperating shoulders, positions a stem guide 26 in axial alignment with the axis of cover 21 and body 28. A seal 25 prevents leakage between members 21 and 28. An enlarged extension of a valve stem 22 passes through and is'axially movable relative to guide member 26. The lower, spherically shaped end of valve stem 22 abuts a discharge controlling shut-off valve member 31 positioned within the body 28. Valve stem 22 is loaded, by a spring 24, against the shut-off valve member 31. Spring 24 is located about stem 22 and held in position by a pair of seating washers 23 whereby the spring is normally in compression. Theload exerted by spring 23 against the enlarged portion of stem 22, and thus against valve member 31, may be adjusted by means of I screw and associated lock nut 19; screw 20 having axial bore for receiving the upper end of stem 22 and the upper seating washer 23 being spring loaded against the lower end of screw 20. Access to the tension adjusting means defined by screw 20 and lock nut 19 is afforded by an end cap 18 which seals the interior of the valve against the environment.

The body portion 28 of pilot valve 2 defines a pair of radial ports by which fluid may be delivered to and discharged from the pilot valve. The first or lower radial port A functions as an inlet port through which operating fluid for the pilot valve is supplied. The upper radial port E functions as a discharge port. A central bore in body portion 28 communicates with ports A and E, in the manner to be described below, and contains the above mentioned discharge shut-off valve member 31, a guide member 29, a pilot piston 30 and an admission shut-off valve member 35. The discharge shut-off valve member 31 is mechanically attached to the upper end of pilot piston 30. Piston 30 moves within the guide member 29. A toroidal seal 33 is, with valve 31 closed, compressed between valve member 31 and the seat defined by the upper end of guide member 29; seal 33 being located in a seal housing in the interest of limiting extrusion of the seal.

As noted above, pilot piston 30 slides in the bore of guide member 29. The pilot piston 30, and the extensions thereof which are connected to shut-off valve members 31 and 35, is provided with an axial bore 52 through which communication is established between the upper chamber 44 disposed above the main portion of pilot piston 30 and the lower chamber 45 which contains the shut-off valve member the upper end of I bore 52 terminating in radial ports in the upper extension of piston 30.

The admission control shut-off valve member 35 is mechanically affixed to the lower extension of pilot piston 30 and limits the travel of the pilot piston. In a preferred embodiment the admission shut-off valve member 35 is threadably engaged on the pilot valve extension and is prevented from rotating by means of a radially extending set screw 37 which has an unthreaded tip. Valve 35 is normally open as shown and, when closed, seats against the bottom of a seat defining member 34. When seated, valve 35 interrupts communication between inlet port A and chamber 45. A seal 27 is provided between seat defining member 34 and base member 36 to insure against leakage.

Pilot piston 30 also defines a bore in which a spring loaded spool valve member 51 moves; spool member 51 traveling in a direction transverse to the main axis of the pilot valve as defined by passage 52 through the pilot piston 30. The design and location of the spool valve may be more clearly seen by reference to FIG. 3. Pressure for positioning spool member 51 is delivered to opposite ends of the transverse bore through pilot piston 30 by means of grooves 53 and 54 formed in piston 30. Spool valve member 51, as may best be seen from FIG. 3, normally prevents flow through passage 52 between chambers and 44.

The third or lower subassembly of pilot valve 2 is, as noted above, defined by a base member 36. In the disclosed embodiment base member 36 is affixed to body member 28 by means of a plurality of socket-headed screws. Base member 36 defines a passage C through which control of the main shut-off valve 1 is achieved in the manner to be described below. Means in the form of an adjustment screw 40 extending into the passage C are provided for limiting the rate of flow to and from the main shut-off valve; a seal 38 being provided about screw 40 to prevent leakage.

In operation of the disclosed embodiment, supply pressure is tapped off the main flow path by conduitprobe 17 upstream of the main shut-off valve and is applied to inlet port A of pilot valve 2 via conduit 46. Through the adjustment of screw 20 and lock nut 19, the force exerted against valve member 31 by the spring loaded stem 22 is selected so that the normal operating pressure will not overcome the spring force and cause opening of discharge shut-off valve 31. The spool valve member 51 is not at this time influenced by the applied pressure since, through the action of grooves 53 and 54, the same pressure is applied to both sides of the spool.

If the applied pressure exceeds the preloading of spring 24, the fluid pressure acting upon the pilot piston 30 becomes greater than the spring force and the shut-off valve member 31 lifts slightly. The slight upward movement of valve member 31 establishes communication between chamber 44 and discharge port E. The venting of chamber 44 establishes a large pressure differential across the pilot piston and causes the snap action closing of shut-off valve 35 thereby interrupting communication between admission port A and valve chamber 45.

When valve member 35 becomes seated there will, however, be communication between port A and the left hand end of valve spool 51 via groove 54. At this time the opposite or spring end of spool 51 will be in communication with chamber 44 thus will be at a pressure, for example atmospheric pressure, maintained at discharge port E. Accordingly, spool valve member 51 will be unbalanced and the spool valve will move to the right thereby opening the axial passage 52 in the pilot piston 30. The opening of axial passage 52 will establish communication between lower chamber 45 and discharge port E.

Thus, with spool valve 51 opened, the pressure in the top chamber 47 of main shut-ofi' valve 1 (see FIG. 1) decays, at a rate determined by the setting of screw 40, to the pressure maintained at exit port E. Accordingly, the main shut-off valve piston 6 will move upwardly under the influence of the supply pressure. As long as the supply pressure remains higher than the normal operating pressure the communication between port C and discharge port E will remain established.

When the applied pressure drops below the preset closing level the force developed by spring 24 will overcome the counteracting fluid forces and pilot piston 30 will move downwardly thereby closing discharge port E and reopening admission port A. The spool member 51 will thereupon return to its original position and the top chamber 47 of the main shut-off valve will be supplied via the pilot valve thereby causing the main shutoff valve piston to return to the closed position shown in FIG. 1.

While a preferred embodiment has been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that this invention has been described by way of illustration and not limitation.

What is claimed is:

1. ln a flow control device including a main fluid operated controller and a pilot valve assembly for controlling the application of control pressure to the actuator of the main controller, the pilot valve assembly comprising a pair of shut-off valve members for respectively controlling admission and discharge of fluid to the pilot valve assembly, said shut-off valves being operated by a pilot valve piston, the improvement comprising:

a spool valve including a spool member which restricts flow between the opposite ends of the pilot valve piston during opening of the discharge controlling shut-off valve, the oppositely disposed faces of said spool valve member being respectively subjected to the pressures prevailing in the chambers at said oppositely disposed ends of said pilot valve piston.

2. The apparatus of claim 1 wherein said pilot valve piston has an axial passage for providing communication between said chambers and wherein said spool valve member normally closes said axial passage.

3. The apparatus of claim 2 wherein said spool valve member is mounted in said pilot valve piston in a bore which extends transversely of and intersects said axial passage.

4. The apparatus of claim 3 wherein said pilot valve piston is provided with grooves which extend between opposite ends of said transverse bore and respective opposite ends of said pilot valve piston.

5. The apparatus of claim 4 wherein said spool valve is spring loaded to the position where said axial passage is closed. 

1. In a flow control device including a main fluid operated controller and a pilot valve assembly for controlling the application of control pressure to the actuator of the main controller, the pilot valve assembly comprising a pair of shutoff valve members for respectively controlling admission and discharge of fluid to the pilot valve assembly, said shut-off valves being operated by a pilot valve piston, the improvement comprising: a spool valve including a spool member which restricts flow between the opposite ends of the pilot valve piston during opening of the discharge controlling shut-off valve, the oppositely disposed faces of said spool valve member being respectively subjected to the pressures prevailing in the chambers at said oppositely disposed ends of said pilot valve piston.
 2. The apparatus of claim 1 wherein said pilot valve piston has an axial passage for providing communication between said chambers and wherein said spool valve member normally closes said axial passage.
 3. The apparatus of claim 2 wherein said spool valve member is mounted in said pilot valve piston in a bore which extends transversely of and intersects said axial passage.
 4. The apparatus of claim 3 wherein said pilot valve piston is provided with grooves which extend between opposite ends of said transverse bore and respective opposite ends of said pilot valve piston.
 5. The apparatus of claim 4 wherein said spool valve is spring loaded to the position where said axial passage is closed. 